Pulse generating circuits



Feb. 20, 1962 D. GLASER 3,022,442

PULSE GENERATING CIRCUITS Filed June 24, 1959 I IP% 26 0--O 26-41 35 35 35 VT 5' |:L '1s \2 MM 20 16 Z I |e 0 3| 0 II \\8l 9 FLIP FLOP 42 38 BLOCKING OSCILLATOR F I g. 1

OUT ou'r OUT TUNED TUNED TUNED cmcurr cnacun' cmcuw 9o I III INVENTOR.

. DAV/D GLHSEE ATTORNEY This invention relates to pulse generating circuits and to circuits for providing an adjustable delay time between a first pulse and a second pulse.

This invention also relates to multi-position electron beam switching tubes and, particularly, to pulse generating circuits for use in generating two time-spaced pulses for use in clearing an electron beam from a position in such a tube and resetting the beam at a selected zero position.

Circuits are known for generating time-spaced pulses, but the best of these circuits use expensive delay lines as components. Others of these circuits which avoid the cost of delay lines are generally unsatisfactory in operation and exhibit poor control of the desired time delay between pulses.

One type of multi-position electron beam switching tube, to which the principles of the invention apply, is described in US. Patent No. 2,721,955 to Fan et al. This type of tube is a magnetron and includes a central cathode which is surrounded by a plurality of groups of electrodes, each group representing a position at which an electron beam may form and from which an output signal may be obtained.

In some applications of these tubes, for example in decade counters or the like, it is desirable to be able to allow the tube to execute a predetermined counting operation, that is, to switch an electron beam from position to position and then, at some selected time, to clear the beam and reset it at a selected zero position. This operation generally requires two electrical pulses, one for clearing the beam and one for resetting it. Circuits are known for clearing and resetting electron beams in tubes of the type described above. However, a universally satisfactory circuit which provides both clear and reset pulses and which provides a variable delay between these pulses is not available. A variable delay is desirable so that the resetting operation may be properly spaced from the clearing operation in each circuit application.

Accordingly, the principles and objects of the present invention are directed toward the provision of improved circuits for providing two or more pulses with variable delay time between them, such pulses being suitable for use in clearing and resetting an electron beam in a multi-position electron beam switching tube.

Briefly, the principles of the invention are described as they relate to a multi-position electron beam tube of the aforementioned type which includes a plurality of positions and which is adapted to switch an electron beam from position to position. Circuit means are provided for producing separate and variably spaced pulses for clearing an electron beam from any position in the tube and resetting the beam at a designated zero position. This circuit means includes first and second electronic devices which are normally not conducting. The two devices are coupled together by a variable resonant circuit including a.

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second output pulse is generated which is coupled to the second electronic device through the tuned circuit. The rate of rise of this output pulse to a predetermined level necessary to turn on the second device is determined by the tuning and the period of the tuned circuit, and, in effect, the time constant of the overall circuit. When the second device is turned on, it produces an output pulse which is the reset pulse and is appropriately applied to the multi-position tube and, if desired, to the driver circuit therefor. The desired time delay between the clear pulse and thereset pulse is thus provided by the resonant coupling circuit.

The principles of the invention may also be employed in a cascade pulse producing device comprising a series of electron discharge devices and resonant circuits connected as described above to produce from a single input pulse, a plurality of controllably spaced output pulses.

The invention is described in greater detail by reference to the drawing wherein:

FIG. 1 is a schematic representation of the tube of FIG. 1 and a circuit in which it may be operated; and

FIG. 2 is a block diagram of a system using some of the elements of FIG. 1 and embodying the principles of the invention.

The circuits and systems described below are particularly suitable for use with a multi-position type 6700 magnetron beam switching tube. in actual construction, this type of tu'be'is cylindrical in form and is shown schematically in linear form as tube 10 in FIG. 1. The tube includes an envelope 12 which contains a central longitudinally elongated cathode 14 and ten groups of electrodes spaced radially equidistantly from the cathode and surrounding the cathode. For simplicity, only four groups of electrodes are shown numbered 0, 1, 2, and 9. Each group of electrodes includes a generally U-shaped elongated spade electrode 16 and a generally L-shaped target electrode 1% positioned so that each target occupies the space between adjacent spade electrodes. Each spade electrode serves to form and hold an electron beam on its corresponding target electrode. A generally rod-like switching electrode 20 is also included in each group of electrodes and is positioned between one edge of each target electrode and the adjacent spade electrode. The switching electrodes are known as switching grids. An open-ended cylindrical permanent magnet (not shown) is provided surrounding the tube envelope and coaxial therewith. The magnet provides an axial magnetic field which is utilized in conjunction with electric fields within the tube to form and switch an electron beam from the cathode to each of the groups of electrodes. The direction in which the beam switches, that is clockwise or counterclockwise, is always the same and is determined by the orientation of the electric and magnetic fields.

Briefly, in operation of tube 10, electrons emitted by the cathode are retained at the cathode if each of the spades, targets and switching grids carries its normal operating electrical potential. When a spade or switching grid experiences a suitable lowering of its potential, an electron beam is formed and directed to the corresponding target electrode. 'The electron beam may be switched from one target electrode to the next by thus suitably altering the electrical potentials of a spade or switching grid. Under normal operating conditions, when ever electrode voltages are such that a beam might be supported at several positions, the beam will switch to the most leading position and lock in at this position.

In the circuit of FIG. 1, the cathode 14 is connected through a suitable resistor 24 to ground. Each of the spade electrodes 16 is coupled through a spade load resistor 26 to a spade buss 28. The spade buss 28 is coupled through a common spade resistor 30 to a suitable positive DC. power supply V of about 200 volts. As-

suming that the position is the one at which an electron beam is to be reset, the spade load resistor is provided as substantially two equal resistors 26. in addition, the 0 spade is coupled to'the anode of a diode 31, the cathode of which is connected to the cathode of the tube 14. The 0 spade is thus clamped to cathode po tential during the reset operation to be described.

The target electrodes 13 are connected through :suitable load resistors 32 to a common target buss 34 which is coupled to a positive .D.C. power supply V of about -300 volts. In addition, an auxiliary output tap 35 is provided at each target for connection to a suitable utilization device or circuit, for example, the cathodes of an indicator tube, or a printing mechanism or the like.

The switching grid electrodes 2t? are connected as follows. The grids at the even-numbered positions are connected together in one set, and the grids at the oddnumbered positions are connected together in another set. Each set of grids is then connected to one of the output leads 36, 3d of a suitable flip-flop driver circuit 40. The

flip-flop is provided with a single input lead 42 which is coupled to one of the control grids of the flip-flop and by which the flip-flop may beset. A source 43 of input or counting pulses is coupled to the flip-flop and each input pulse from the source causes the flip-lop to generate an output pulse, the output pulses appearing alternately on first one and then the other of the output leads 36 and 38. These output pulses operate the switching grids successively and cause an electron beam toswitch from position to position in the tube 10.

According to the invention, novel circuit means are provided for generating pairs of pulses having adjustable and variable time delay between the pulses. The pulses of each pair are used to clearan electron beam from any position in the tube 19 and reset the beam at a selected zero position. The flip-flop driver may also be reset at the same time as the tube 1d. This circuit means includes a first thyratron 44 having a cathode 46, control grid 4%, shield grid t and anode 52. The cathode 44 is connected through a bias resistor 54 to ground, and it is also coupled by lead 55 through a capacitor 56 and to the "cathode 14 of the tube It). The control grid 48 and shield grid 50 are connected through resistors 58 and '60, respectively, to a common lead 62 which is coupled through a capacitor 64 to the output of a suitable pulse- .producing driver circuit, for example, a blocking oscillator 66. The shield grid 50 is also coupled through a -first resistor 68 to a negative D.C. supply voltage of about 150 volts and through a second resistor 7b to ground. The-anode 52 is coupled through a capacitor '72 to ground and through a quenching resistor 74 to a positive supply voltage of about 300 volts.

According to the invention, the anode 52 is also connected to an adjustable series or parallel resonant circuit, shown in FIG. 1 as a series resonant circuit 7d, including a capacitor 78 and an inductor 80, at least one of which 'is variable but both of which may be variable. The inductor 80 is connected to the junction point 82 of resistors 84 and 86, one of which goes to ground and the other of which goes to a negative DC. power supply of about 150 volts. The junction point 82 of the two resistors 84 and 86 is also connected through a capacitor 88 to ground.

The circuit of FIG. 1 includes'a second thyratron 99 having a cathode 92, control grid 94, shield grid 6 and anode 98. The cathode 92 is connected through a bias resistor 190 to ground. The control grid $4 and shield grid 96 are connected through resistors 1M and 1%,

"respectively, to a common lead 1% which is connected to the junction point 119 between the capacitor 73 and inductor 8'!) of the tuned circuit 76. The anode 98 is coupled through a capacitor 112 to ground and through a quenching resistor 114 toa positive supply voltage of a'bout'300 volts. The anode 98 is also coupled to a capacitor 116 whichis connected both through a resistor 'to a positiveD.C.'p'oW'er supply of'about 150 volts'and 4:- to the input lead 42 of the flip-flop circuit 40. The capacitor 116 is also coupled by a lead 120 to the junction point of the two resistors 26' coupled to the 0 spade.

In operation of the circuit of FIG. 1, initially the circuit parameters and bias voltages coupled to the two thyratrons 44 and 9% are so arranged that both thyratro'ns are not conducting. At the same time, .it is assumed that input pulses .from the source 43 .are applied to the flip-flop 4i) and a beam is being switched from position to position in the tube it in response to output pulses from the flip-flop applied to the switching gridelectrodes 20. When it is desired to clear the beam from Whatever position it may occupy in the tube .10 and reset it'at the 0 position, the blocking oscillator 66 is triggered and a positive pulse 122 of about volts produced thereby is applied to the grids of the thyratron 44. This pulse is of sufilcient amplitude to cause the thyratron to fire, and the resultant current flow produces a sharply peaked positive clear pulse 124 of about 150 volts at the cathode lead 55 and a'negative pulse 126 of about 150 volts at the anode of the thyratron. The positive pulse 124 which appears at the cathode is coupled through-the capacitor as to the'cathode 14 ot the tube 10 and raises the potential of the cathode 14 sufficiently positive to cause an electron beam to clear.

At the same time, the negative pulse 126 at the anode 52 passes through the tuned resonant circuit 7'6 and produces across the inductor 8d a damped oscillating pulse 12% of the type shown which is applied to the grids of the second thyratron it. This pulse 128 includes a first cycle which has a negative first half-cycle and a positive second half-cycle. Assuming that the second thyratron 90 is biased to be tired at a positive voltage represented at point 1.3% on the wave, when the wave reaches this point and the voltage represented thereby is applied to the grids of the thyratron 96, the thyratron fires and produces a negative pulse 132 at the anode 98 which is applied to and sets the fiip-fiop 40 in a desired initial state. .At the same time, the pulse132 is applied to the .0 spade of the tube 10 and lowers the potential of this spade sufiiciently to cause an electron beam to form at the 0 position. The diodefil serves to clamp the 0'spade at cathode potential during the reset operation so that, if the reset pulse is more negative than the cathode potential, then the 0 spade will not be afiected'thereby and will be reducedin potential no lower than the cathode potential. This insures properresetting ofthe beam.

Thus, the tube It} .is cleared'by thepulse 124 and reset by the pulse 132,.and the timedelay between these pulses is controlled by the resonant circuit including capacitor 78and inductor 80. The time delay between the clear and reset pulses may be varied by adjusting either the capacitor or inductor or both, as desired.

The principles of the invention may be employed in a cascade multiple stagesystem wherein a single input pulse maybe used to provide a plurality of randomly and controllably spaced output pulses. The output pulses may be used to control the operation of a beam switching tube as shown in FIG. 1, or they may be used in any other suitable manner. Such a system is shown in FIG. .2 .and includes a first'thyratron 44' provided with suitable circuit elements as shown in FIG. 1 and having its output coupledtoa variable tuned circuit 76 having an adjustable period as the tuned circuit 76 in FIG. 1. The tuned circuit 7a is connected to the input of a second thyratron '94), the output of which is connected to a terminal from which a pulse may be taken. The output of the'thyratron 90' is also connected to a' variable tuned'circuit 76" which is connected to the input of a thyratron tl". "The thyratron 5 0" is provided with an output terminal from which a pulse'may be taken and the output is also con- 'nected to the next variabletuned circuit'76 which is connected'in turn to the input of a thyratron 90". The 'thyratron 96 is'provided'with an output terminal and 5 may also be connected to another tuned circuit, and so forth. The system of FIG. 2 is operated as in FIG. 1 with each thyratron capable of providing an output pulse with the spacing of the output pulses being determined by adjustment of the various tuned circuits.

What is claimed is:

1. A beam clearing and resetting circuit for a magnetron beam switching tube including first and second electron discharge devices each having a cathode, a control grid, and an anode; means normally biasing said devices in an oit condition; an adjustable resonant circuit coupled between said discharge devices and coupling the output of the first device to the input of the second, the adjustment of said resonant circuit determining the time delay between the turning on of the first device and the turning on of the second device; a magnetron beam switching tube having a cathode and a plurality of groups of electrodes; each group including a target electrode which receives an electron beam and produces an output signal therefrom, a spade electrode which holds an electron beam on its associated target electrode, and a switching electrode which serves to switch an electron beam from one group of electrodes to the next; the cathode of said first device being coupled to the cathode of said beam switching tube whereby a positive beam clearing pulse is applied thereto when said first device is turned on; the anode of said first device being coup-led through said resonant circuit to the control grid of said second device whereby said second device is turned on after a time delay determined by the tuning of said resonant circuit; and the anode of said second discharge device being coupled to the spade electrode of one of said groups of electrodes for coupling a negative pulse thereto and forming an electron beam thereat.

2. The circuit defined in claim 1 wherein said first and second discharge devices comprise thyratrons.

3. The circuit defined in claim 1 and including a driver circuit coupled to the switching electrodes of said beam switching tube, the anode of said second discharge device being coupled to said driver circuit to set it in an initial operating state at the same time that a beam is reset in said beam switching tube whereby said driver circuit is set to switch a beam from position to position in said beam switching tube.

4. The circuit of claim 3 wherein said driver circuit is a flip-flop.

References Cited in the file of this patent UNITED STATES PATENTS 2,408,086 Meacham et al Sept. 24, 1946 2,418,375 Tourshou Apr. 1, 1947 2,730,658 Six Ian. 10, 1956 2,819,395 Jones Jan. 7, 1958 2,856,558 Cola Oct. 14, 1958 2,890,333 Zinn June 9, 1959 

